After graduating from the Infantry Officer School in 1910 with the rank of 2nd lieutenant, he fought in the Second Balkan War and in World War I, being promoted to major. He became colonel in 1934, and brigadier general in 1939.

On April 12, 1945, Lascăr became commander of the Horia, Cloșca și Crișan Division; the political commissar attached to this Soviet-organized unit was the Communist activist Valter Roman. On September 12, 1945, Lascăr was named commander of the Fourth Army. He was a leader of the Electoral Commission of the Army, in advance of the general election of November 19, 1946. After a coalition led by the Romanian Communist Party won the election (through widespread intimidation tactics and electoral fraud), he was appointed Minister of Defense, holding this ministerial portfolio from November 29, 1946 until December 27, 1947, when he was replaced by Emil Bodnăraș. He was then Inspector-General of the Romanian Army until January 12, 1950, when he was discharged from active duty.

On June 7, 1947, he signed the decree establishing the football club Asociația Sportivă a Armatei București, now FC Steaua București.